An Elastin-derived composite matrix for enhanced vascularized and innervated bone tissue reconstruction: from material development to preclinical evaluation.

Despite progress in bone tissue engineering, reconstruction of large bone defects remains an important clinical challenge. Here, we developed a biomaterial designed to recruit bone cells, endothelial cells, and neuronal fibers within the same matrix, enabling bone tissue regeneration. The bioactive matrix is based on modified elastin-like polypeptides (ELPs) grafted with laminin-derived adhesion peptides IKVAV and YIGSR, and the SNA15 peptide for retention of hydroxyapatite (HA) particles. The composite matrix shows suitable porosity, interconnectivity, biocompatibility for endothelial cells, and the ability to support neurites outgrowth by sensory neurons. Subcutaneous implantation led to the formation of osteoid tissue, characterized by the presence of bone cells, vascular networks, and neuronal structures, while minimizing inflammation. Using a rat femoral condyle defect model, we performed longitudinal micro-CT analysis, which demonstrates a significant increase in the volume of mineralized tissue when using the ELP-based matrix compared to empty defects and a commercially available control (Collapat). Furthermore, visible blood vessel networks and nerve fibers are observed within the lesions after a period of two weeks. By incorporating multiple key components that support cell growth, mineralization, and tissue integration, this ELP-based composite matrix provides a holistic and versatile solution to enhance bone tissue regeneration. This article is protected by copyright. All rights reserved.

[Uses of 3D printing and Bioprinting for pre-implant bone reconstruction in Oral Surgery]. / Impression 3D et bioimpression pour la régénération osseuse en chirurgie orale.

Pre-implant bone surgery in oral surgery allows to reconstruct maxillary atrophies related to traumatic, infectious or tumoral processes. In this context, the ideal biomaterial remains autogenous bone, but biomaterials (of natural or synthetic origin) allow to limit the morbidity linked to bone harvesting, and to simplify these surgical procedures. In this article, we illustrate how 3D printing technologies can be used as an adjuvant to treat bone defects of complex shape or to create anatomical models used to plan interventions. Finally, some perspectives brought by tissue engineering and bioprinting (creation of complex in vitro models) are presented.

Title: Impression 3D et bioimpression pour la régénération osseuse en chirurgie orale. Abstract: La chirurgie osseuse pré-implantaire en chirurgie orale permet de reconstruire les atrophies des maxillaires en rapport avec des processus traumatiques, infectieux ou tumoraux. Dans ce contexte, le biomatériau idéal reste l'os autogène mais les biomatériaux (d'origine naturelle ou synthétique) permettent de limiter la morbidité liée aux prélèvements osseux et de simplifier ces interventions chirurgicales. Dans cet article, nous illustrons l'apport récent de l'impression 3D dans ce contexte pour traiter des défauts osseux de forme complexe ou pour créer des modèles anatomiques servant à planifier les interventions. Enfin, les perspectives apportées par l'ingénierie tissulaire et la bioimpression (création de modèles in vitro complexes) sont détaillées.

Development of Novel Polysaccharide Membranes for Guided Bone Regeneration: In Vitro and In Vivo Evaluations.

INTRODUCTION: Guided bone regeneration (GBR) procedures require selecting suitable membranes for oral surgery. Pullulan and/or dextran-based polysaccharide materials have shown encouraging results in bone regeneration as bone substitutes but have not been used to produce barrier membranes. The present study aimed to develop and characterize pullulan/dextran-derived membranes for GBR. MATERIALS AND METHODS: Two pullulan/dextran-based membranes, containing or not hydroxyapatite (HA) particles, were developed. In vitro, cytotoxicity evaluation was performed using human bone marrow mesenchymal stem cells (hBMSCs). Biocompatibility was assessed on rats in a subcutaneous model for up to 16 weeks. In vivo, rat femoral defects were created on 36 rats to compare the two pullulan/dextran-based membranes with a commercial collagen membrane (Bio-Gide®). Bone repair was assessed radiologically and histologically. RESULTS: Both polysaccharide membranes demonstrated cytocompatibility and biocompatibility. Micro-computed tomography (micro-CT) analyses at two weeks revealed that the HA-containing membrane promoted a significant increase in bone formation compared to Bio-Gide®. At one month, similar effects were observed among the three membranes in terms of bone regeneration. CONCLUSION: The developed pullulan/dextran-based membranes evidenced biocompatibility without interfering with bone regeneration and maturation. The HA-containing membrane, which facilitated early bone regeneration and offered adequate mechanical support, showed promising potential for GBR procedures.

Oral potentially malignant disorders - An assessment of knowledge and attitude to future education in undergraduate dental students.

INTRODUCTION: The aim of this study was to assess the knowledge and clinical experience of oral potentially malignant disorders (OPMDs) in undergraduate dental students in six European countries (Croatia, France, Italy, Portugal, Spain and United Kingdom) and assess student's attitude and preference to future education on the topic. A secondary aim was to identify gaps in student's knowledge and clinical practice. The study was a part of the Erasmus+ project "Oral Potentially Malignant Disorders: Healthcare Professionals Training" (Grant No: 2020-1-UK01-KA202-078917). MATERIALS AND METHODS: An online questionnaire was distributed to all final-year students in six partner universities. This consisted of four parts assessing: (1) knowledge on OPMDs, (2) clinical experience with this group of patients, (3) self-rated competence in the management of OPMDs and (4) preferences with regard to future education. RESULTS: Two hundred and sixty final-year dental students from six partner universities responded to the questionnaire. Response rates varied from 12% to 92% between partner universities. Significant differences in clinical experience and knowledge were found between students. Students with more clinical exposure to OPMDs rated their knowledge and competence in the management of OPMDs higher than students with less clinical experience. The majority of students were interested in future education on OPMDs, preferably via short educational videos. CONCLUSION: The majority of students have received theoretical knowledge of OPMDs during their undergraduate studies, however, not all had clinical exposure to this group of patients. Students were open to further education on OPMDs. Important deficiencies in knowledge were identified that need to be addressed and it is anticipated that the e-learning platform and e-book that are in development by partner institutions will help to improve overall knowledge of OPMDs.

Malignant Transformation Rate of Oral Submucous Fibrosis: A Systematic Review and Meta-Analysis.

Oral submucous fibrosis (OSF) is a chronic progressive condition affecting the oral cavity, oropharynx and upper third of the oesophagus. It is a potentially malignant disorder. The authors collated and analysed the existing literature to establish the overall malignant transformation rate (MTR). A retrospective analysis of medical and dental scientific literature using online indexed databases was conducted for the period 1956 to 2021. The quality of the enrolled studies was assessed by the Newcastle-Ottawa Scale (NOS). A meta-analysis using a random effects model of a single proportion was performed along with statistical tests for heterogeneity. The overall proportion of malignancy across all studies was 0.06 (95% CI, 0.02-0.10), indicating an overall 6% risk of malignant transformation across all studies and cohorts. Sub-group analyses revealed strong differences in proportion of malignancy according to ethnicity/cohort; Chinese = 0.02 (95% CI 0.01-0.02), Taiwanese = 0.06 (95% CI, 0.03-0.10), Indian = 0.08 (95% CI, 0.03-0.14) and Pakistani = 0.27 (95% CI 0.25-0.29). Overall, the MTR was 6%; however, wide heterogeneity of the included studies was noted. Geographic variations in MTR were noted but were not statistically significant. Further studies are required to analyse the difference between cohort groups.

Accuracy of commercial 3D printers for the fabrication of surgical guides in dental implantology.

OBJECTIVES: To evaluate the accuracy of two different surgical guides (small extent = single implant and large extent = full arch) fabricated by five additive manufacturing technologies (SLA=Stereolithography, DLP= Digital Light Processing, FDM=Fused Deposition Modeling, SLS=Selective Laser Sintering, Inkjet). METHODS: Overall, 72 guides (6 per type) were obtained with the different machines (SLA=Form2; DLP=Rapid Shape D40 and Cara Print 4.0; FDM=Raise 3D Pro2; SLS=Prodways P1000; Polyjet®=Stratasys J750). The guides were surface-scanned with an optical dental scanner, and the resulting files were compared with the initial design files using a surface matching software. Root Mean Square (RMS) and standard deviation were calculated, representing respectively trueness and precision. Kruskall-Wallis non-parametric test was used to compare trueness and precision between small-extent and large-extent guides and 3D printer by pairs. The threshold for significance was α=0.05, except for the comparison of printers by pairs where a Bonferroni-corrected level of 0.0033 was used. RESULTS: Significant differences were observed for trueness and precision between small-extent and large-extent guides, regardless the printer except for DLP (trueness and precision) and SLS (precision). SLA, DLP and Polyjet® technologies showed similar results in terms of trueness and precision for both small-extend and large-extend guides (P>0.05). CONCLUSIONS: The size affected the accuracy of CAD-CAM surgical guides. The different additive manufacturing technologies had a limited impact on the accuracy. CLINICAL SIGNIFICANCE: This study is of clinical interest as it shows that the 3D printing technology (SLA/DLP) has a limited impact on 3D printed surgical guides accuracy. However, the size of the guide can have a significant impact, as small-extent guides were more accurate than large-extent guides.

Bone regeneration in both small and large preclinical bone defect models using an injectable polymer-based substitute containing hydroxyapatite and reconstituted with saline or autologous blood.

Microbeads consisting of pullulan and dextran supplemented with hydroxyapatite have recently been developed for bone tissue engineering applications. Here, we evaluate the bone formation in two different preclinical models after injection of microbeads reconstituted with either saline buffer or autologous blood. Addition of saline solution or autologous blood to dried microbeads packaged into syringes allowed an easy injection. In the first rat bone defect model performed in the femoral condyle, microcomputed tomography performed after 30 and 60 days revealed an important mineralization process occurring around and within the core of the microbeads in both conditions. Bone volume/total volume measurements revealed no significant differences between the saline solution and the autologous blood groups. Histologically, osteoid tissue was evidenced around and in contact of the microbeads in both conditions. Using the sinus lift model performed in sheep, cone beam computed tomography revealed an important mineralization inside the sinus cavity for both groups after 3 months of implantation. Representative Masson trichrome staining images showed that bone formation occurs at the periphery and inside the microbeads in both conditions. Quantitative evaluation of the new bone formation displayed no significant differences between groups. In conclusion, reconstitution of microbeads with autologous blood did not enhance the regenerative capacity of these microbeads compared to the saline buffer group. This study is of particular interest for clinical applications in oral and maxillofacial surgery.

Chorion and amnion/chorion membranes in oral and periodontal surgery: A systematic review.

The aim of this study was to perform a systematic review on the clinical applications where chorion membrane (CM) and amnion/chorion membrane (ACM) were used for oral tissue regeneration procedures. Selection of articles was carried out by two evaluators in Pubmed and Scopus databases, and Outcomes (PICO) method was used to select the relevant articles. Clinical studies reporting the use of CM or ACM for oral soft and hard tissue regeneration were included. The research involved 21 studies conducted on 375 human patients. Seven clinical applications of CM and ACM in oral and periodontal surgery were identified: gingival recession treatment, intrabony and furcation defect treatment, alveolar ridge preservation, keratinized gum width augmentation around dental implants, maxillary sinus membrane repair, and large bone defect reconstruction. CM and ACM were compared to negative controls (conventional surgeries without membrane) or to the following materials: collagen membranes, dense polytetrafluoroethylene membranes, platelet-rich fibrin membranes, amnion membranes, and to a bone substitute. Several studies support the use of CM and ACM as an efficient alternative to current techniques for periodontal and oral soft tissue regeneration procedures. However, further studies are necessary to increase the level of evidence and especially to demonstrate their role for bone regeneration.

Correction to: 3D printed bone models in oral and craniomaxillofacial surgery: a systematic review.

An amendment to this paper has been published and can be accessed via the original article.

3D printed bone models in oral and cranio-maxillofacial surgery: a systematic review.

AIM: This systematic review aimed to evaluate the use of three-dimensional (3D) printed bone models for training, simulating and/or planning interventions in oral and cranio-maxillofacial surgery. MATERIALS AND METHODS: A systematic search was conducted using PubMed® and SCOPUS® databases, up to March 10, 2019, by following the Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) protocol. Study selection, quality assessment (modified Critical Appraisal Skills Program tool) and data extraction were performed by two independent reviewers. All original full papers written in English/French/Italian and dealing with the fabrication of 3D printed models of head bone structures, designed from 3D radiological data were included. Multiple parameters and data were investigated, such as author's purpose, data acquisition systems, printing technologies and materials, accuracy, haptic feedback, variations in treatment time, differences in clinical outcomes, costs, production time and cost-effectiveness. RESULTS: Among the 1157 retrieved abstracts, only 69 met the inclusion criteria. 3D printed bone models were mainly used as training or simulation models for tumor removal, or bone reconstruction. Material jetting printers showed best performance but the highest cost. Stereolithographic, laser sintering and binder jetting printers allowed to create accurate models with adequate haptic feedback. The cheap fused deposition modeling printers exhibited satisfactory results for creating training models. CONCLUSION: Patient-specific 3D printed models are known to be useful surgical and educational tools. Faced with the large diversity of software, printing technologies and materials, the clinical team should invest in a 3D printer specifically adapted to the final application.

Assessment of fresh and preserved amniotic membrane for guided bone regeneration in mice.

Thanks to its biological properties, the human amniotic membrane (HAM) can be used as a barrier membrane for guided bone regeneration (GBR). However, no study has assessed the influence of the preservation method of HAM for this application. This study aimed to establish the most suitable preservation method of HAM for GBR. Fresh (F), cryopreserved (C) lyophilized (L), and decellularized and lyophilized (DL) HAM were compared. The impact of preservation methods on collagen and glycosaminoglycans (GAG) content was evaluated using Masson's trichrome and alcian blue staining. Their suture retention strengths were assessed. In vitro, the osteogenic potential of human bone marrow mesenchymal stromal cells (hBMSCs) cultured on the four HAMs was evaluated using alkaline phosphatase staining and alizarin red quantification assay. In vivo, the effectiveness of fresh and preserved HAMs for GBR was assessed in a mice diaphyseal bone defect after 1 week or 1 month healing. Micro-CT and histomorphometric analysis were performed. The major structural components of HAM (collagen and GAG) were preserved whatever the preservation method used. The tearing strength of DL-HAM was significantly higher. In vitro, hBMSCs seeded on DL-HAM displayed a stronger ALP staining, and alizarin red staining quantification was significantly higher at Day 14. In vivo, L-HAM and DL-HAM significantly enhanced early bone regeneration. One month after the surgery, only DL-HAM slightly promoted bone regeneration. Several preserving methods of HAM have been studied for bone regeneration. Here, we have demonstrated that DL-HAM achieved the most promising results for GBR.

Layer-by-layer bioassembly of poly(lactic) acid membranes loaded with coculture of HBMSCs and EPCs improves vascularization in vivo.

Layer-by-layer (LBL) BioAssembly method was developed to enhance the control of cell distribution within 3D scaffolds for tissue engineering applications. The objective of this study was to evaluate in vivo the development of blood vessels within LBL bioassembled membranes seeded with human primary cells, and to compare it to cellularized massive scaffolds. Poly(lactic) acid (PLA) membranes fabricated by fused deposition modeling were seeded with monocultures of human bone marrow stromal cells or with cocultures of these cells and endothelial progenitor cells. Then, four cellularized membranes were assembled in LBL constructs. Early osteoblastic and endothelial cell differentiation markers, alkaline phosphatase, and von Willebrand's factor, were expressed in all layers of assemblies in homogenous manner. The same kind of LBL assemblies as well as cellularized massive scaffolds was implanted subcutaneously in mice. Human cells were observed in all scaffolds seeded with cells, but not in the inner parts of massive scaffolds. There were significantly more blood vessels observed in LBL bioassemblies seeded with cocultures compared to all other samples. LBL bioassembly of PLA membranes seeded with a coculture of human cells is an efficient method to obtain homogenous cell distribution and blood vessel formation within the entire volume of a 3D composite scaffold.

Micropatterning of endothelial cells to create a capillary-like network with defined architecture by laser-assisted bioprinting.

Development of a microvasculature into tissue-engineered bone substitutes represents a current challenge. Seeding of endothelial cells in an appropriate environment can give rise to a capillary-like network to enhance prevascularization of bone substitutes. Advances in biofabrication techniques, such as bioprinting, could allow to precisely define a pattern of endothelial cells onto a biomaterial suitable for in vivo applications. The aim of this study was to produce a microvascular network following a defined pattern and preserve it while preparing the surface to print another layer of endothelial cells. We first optimise the bioink cell concentration and laser printing parameters and then develop a method to allow endothelial cells to survive between two collagen layers. Laser-assisted bioprinting (LAB) was used to pattern lines of tdTomato-labeled endothelial cells cocultured with mesenchymal stem cells seeded onto a collagen hydrogel. Formation of capillary-like structures was dependent on a sufficient local density of endothelial cells. Overlay of the pattern with collagen I hydrogel containing vascular endothelial growth factor (VEGF) allowed capillary-like structures formation and preservation of the printed pattern over time. Results indicate that laser-assisted bioprinting is a valuable technique to pre-organize endothelial cells into high cell density pattern in order to create a vascular network with defined architecture in tissue-engineered constructs based on collagen hydrogel.

Guided Implant Surgery to Reduce Morbidity in Von Willebrand Disease Patients: A Case Report.

INTRODUCTION: Von Willebrand Disease is the most common inherited bleeding disorder. In the general population, 1/8000 patients are affected. Primary hemostasis (platelet adhesion) and coagulation (protection of Factor VIII) are altered. Among several bleeding symptoms, these patients suffer from excessive bleeding of oral mucosa and dental management requires a close collaboration between haematologists and oral surgeons. MATERIALS & METHODS: Guided implant surgery can be used to increase the accuracy of implant placement and to reduce the overall morbidity of this surgical procedure by using a flapless surgery technique. CASE REPORT: We report the case of a 49 years old woman having a Type 2A von Willebrand disease and who presented to replace tooth #.46 because of interradicular fracture and peri-apical infection. After planning the implant surgery using Codiagnostix® software, a surgical guide was prepared. The patient received 4 injections of von Willebrand factor (Willfactin®) for this particular surgical procedure. The implant was placed immediately after tooth removal and local haemostasis was performed. DISCUSSION: The follow-up was uneventful and the implant was restored by a crown 4 months later. Two cases of implant placement in haemophiliac patients have been reported before in the literature. CONCLUSION: As far as we know, this is the first case report of implant placement in a patient having a von Willebrand disease. The use of guided surgery allowed to perform a mini-invasive procedure and thus contributed to prevent bleeding complications in this patient.

Characterization of printed PLA scaffolds for bone tissue engineering.

Autografts remain the gold standard for orthopedic transplantations. However, to overcome its limitations, bone tissue engineering proposes new strategies. This includes the development of new biomaterials such as synthetic polymers, to serve as scaffold for tissue production. The objective of this present study was to produce poly(lactic) acid (PLA) scaffolds of different pore size using fused deposition modeling (FDM) technique and to evaluate their physicochemical and biological properties. Structural, chemical, mechanical, and biological characterizations were performed. We successfully fabricated scaffolds of three different pore sizes. However, the pore dimensions were slightly smaller than expected. We found that the 3D printing process induced decreases in both, PLA molecular weight and degradation temperatures, but did not change the semicrystalline structure of the polymer. We did not observe any effect of pore size on the mechanical properties of produced scaffolds. After the sterilization by γ irradiation, scaffolds did not exhibit any cytotoxicity towards human bone marrow stromal cells (HBMSC). Finally, after three and seven days of culture, HBMSC showed high viability and homogenous distribution irrespective of pore size. Thus, these results suggest that FDM technology is a fast and reproducible technique that can be used to fabricate tridimensional custom-made scaffolds for tissue engineering. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 887-894, 2018.

Web-Based Information on the Treatment of Tobacco Dependence for Oral Health Professionals: Analysis of English-Written Websites.

BACKGROUND: Studies have been conducted on the content and quality of Web-based information for patients who are interested in smoking cessation advice and for health care practitioners regarding the content of e-learning programs about tobacco cessation. However, to the best of our knowledge, there is no such information about the quality of Web-based learning resources regarding smoking cessation dedicated to oral health professionals. OBJECTIVE: The aim of this study was to identify and evaluate the quality of the content of webpages providing information about smoking cessation for oral health care professionals. METHODS: Websites were identified using Google and Health on Net (HON) search engines using the terms: smoking cessation OR quit smoking OR stop smoking OR 3As OR 5As OR tobacco counselling AND dentistry OR dental clinic OR dentist OR dental hygienist OR oral health professionals. The first 100 consecutive results of the 2 search engines were considered for the study. Quality assessment was rated using the DISCERN questionnaire, the Journal of the American Medical Association (JAMA) benchmarks, and the HON seal. In addition, smoking cessation content on each site was assessed using an abbreviated version of the Smoke Treatment Scale (STS-C) and the Smoking Treatment Scale-Rating (STS-R). To assess legibility of the selected websites, the Flesch Reading Ease (FRES) and the Flesch-Kinkaid Reading Grade Level (FKRGL) were used. Websites were also classified into multimedia and nonmultimedia and friendly and nonfriendly usability. RESULTS: Of the first 200 sites selected (100 of Google and 100 of HON), only 11 met the inclusion criteria and mainly belonged to governmental institutions (n=8), with the others being prepared by Professional Associations (n=2) and nonprofit organizations (n=1). Only 3 were exclusively dedicated to smoking cessation. The average score obtained with the DISCERN was 3.0, and the average score in the FKRGL and FRES was 13.31 (standard deviation, SD 3.34) and 40.73 (SD 15.46), respectively. Of the 11 websites evaluated, none achieved all the four JAMA benchmarks. The mean score of STS-R among all the websites was 2.81 (SD 0.95) out of 5. A significant strong positive correlation was obtained between the DISCERN mean values and the STS-R (R=.89, P=.01). CONCLUSIONS: The mean quality of webpages with information for oral health care professionals about smoking cessation is low and displayed a high heterogeneity. These webpages are also difficult to read and often lack multimedia resources, which further limits their usefulness.

In situ printing of mesenchymal stromal cells, by laser-assisted bioprinting, for in vivo bone regeneration applications.

Bioprinting has emerged as a novel technological approach with the potential to address unsolved questions in the field of tissue engineering. We have recently shown that Laser Assisted Bioprinting (LAB), due to its unprecedented cell printing resolution and precision, is an attractive tool for the in situ printing of a bone substitute. Here, we show that LAB can be used for the in situ printing of mesenchymal stromal cells, associated with collagen and nano-hydroxyapatite, in order to favor bone regeneration, in a calvaria defect model in mice. Also, by testing different cell printing geometries, we show that different cellular arrangements impact on bone tissue regeneration. This work opens new avenues on the development of novel strategies, using in situ bioprinting, for the building of tissues, from the ground up.

Layer-by-layer bioassembly of cellularized polylactic acid porous membranes for bone tissue engineering.

The conventional tissue engineering is based on seeding of macroporous scaffold on its surface ("top-down" approach). The main limitation is poor cell viability in the middle of the scaffold due to poor diffusion of oxygen and nutrients and insufficient vascularization. Layer-by-Layer (LBL) bioassembly is based on "bottom-up" approach, which considers assembly of small cellularized blocks. The aim of this work was to evaluate proliferation and differentiation of human bone marrow stromal cells (HBMSCs) and endothelial progenitor cells (EPCs) in two and three dimensions (2D, 3D) using a LBL assembly of polylactic acid (PLA) scaffolds fabricated by 3D printing. 2D experiments have shown maintain of cell viability on PLA, especially when a co-cuture system was used, as well as adequate morphology of seeded cells. Early osteoblastic and endothelial differentiations were observed and cell proliferation was increased after 7 days of culture. In 3D, cell migration was observed between layers of LBL constructs, as well as an osteoblastic differentiation. These results indicate that LBL assembly of PLA layers could be suitable for BTE, in order to promote homogenous cell distribution inside the scaffold and gene expression specific to the cells implanted in the case of co-culture system.

The proangiogenic potential of a novel calcium releasing composite biomaterial: Orthotopic in vivo evaluation.

Insufficient angiogenesis remains a major hurdle in current bone tissue engineering strategies. An extensive body of work has focused on the use of angiogenic factors or endothelial progenitor cells. However, these approaches are inherently complex, in terms of regulatory and methodologic implementation, and present a high cost. We have recently demonstrate the potential of electrospun poly(lactic acid) (PLA) fiber-based membranes, containing calcium phosphate (CaP) ormoglass particles, to elicit angiogenesis in vivo, in a subcutaneous model in mice. Here we have devised an injectable composite, containing CaP glass-ceramic particles, dispersed within a (Hydroxypropyl)methyl cellulose (HPMC) matrix, with the capacity to release calcium in a more sustained fashion. We show that by tuning the release of calcium in vivo, in a rat bone defect model, we could improve both bone formation and increase angiogenesis. The bone regeneration kinetics was dependent on the Ca2+ release rate, with the faster Ca2+ release composite gel showing improved bone repair at 3weeks, in relation to control. In the same line, improved angiogenesis could be observed for the same gel formulation at 6weeks post implantation. This methodology allows to integrate two fundamental processes for bone tissue regeneration while using a simple, cost effective, and safe approach. STATEMENT OF SIGNIFICANCE: In current bone tissue engineering approaches the achievement of sufficient angiogenesis, during tissue regeneration, is a major limitation in order to attain full tissue functionality. Recently, we have shown that calcium ions, released by the degradation of calcium phosphate ormoglasses (CaP), are effective angiogenic promoters, in both in vitro and in a subcutaneous implantation model. Here, we devised an injectable composite, containing CaP glass-ceramic particles, dispersed within a HPMC matrix, enabling the release of calcium in a more sustained fashion. We show that by tuning the release of calcium in vivo, in a rat bone defect model, we could improve both bone formation and increase angiogenesis. This simple and cost effective approach holds great promise to translate to the clinics.

Patterning of Endothelial Cells and Mesenchymal Stem Cells by Laser-Assisted Bioprinting to Study Cell Migration.

Tissue engineering of large organs is currently limited by the lack of potent vascularization in vitro. Tissue-engineered bone grafts can be prevascularized in vitro using endothelial cells (ECs). The microvascular network architecture could be controlled by printing ECs following a specific pattern. Using laser-assisted bioprinting, we investigated the effect of distance between printed cell islets and the influence of coprinted mesenchymal cells on migration. When printed alone, ECs spread out evenly on the collagen hydrogel, regardless of the distance between cell islets. However, when printed in coculture with mesenchymal cells by laser-assisted bioprinting, they remained in the printed area. Therefore, the presence of mesenchymal cell is mandatory in order to create a pattern that will be conserved over time. This work describes an interesting approach to study cell migration that could be reproduced to study the effect of trophic factors.